The present invention is directed to certain new polyamino-polyphosphono hydroxybenzenesulfonic acid compounds and to aqueous compositions containing said compounds. Specifically, the novel compounds of the present invention are 3,5-bis(1,1-diphosphonoalkylaminomethyl)-4-hydroxybenzenesulfonic acid and 3-(1,1-diphosphonoalkylaminomethyl)-4-hydroxybenzenesulfonic acid.
The subject compounds either singly or in combination, can be incorporated into aqueous solutions (normally as a metal salt) and utilized as a metal chelant to prevent scale and corrosion formation in aqueous systems.
Various organic acid compounds have been synthesized to provide a material useful as a scale and corrosion inhibiting agent. These agents contain various organic groups in certain stereoconfiguration to provide the ability to act as a chelant for metal ions.
Amino acids are well known to provide chelant properties. For example, U.S. Pat. No. 2,673,213 teaches that polyamino acids of carboxylic, phosphonic or sulfuric acids are capable of reacting with relevant metal ions to form the chelant. DE 20 48 9 13 and 26 25 767 teach that 1-amino-1,1-diphosphonic acid are capable of complexing with metal ions and that they can be formed by reacting an organic nitrile with phosphorous acid in the presence of HX or at elevated temperatures in the absence of HX.
The desire to incorporate hydroxyalkyl functional groups into phosphonic acid metal chelating compounds is described in U.S. Pat. No. 3,398,198. This reference suggests that hydroxyalkyl groups can be substituted for a hydrogen of an amine by reaction with an alkylene oxide (e.g. propylene oxide).
Various amino-phosphonic-sulfonic acids are taught in U.S. Pat. Nos. 4,085,134; 4,312,736; and 4,229,294. These patents are directed to compounds having the general formula: ##STR1## where N is an amine group and n and m are each at least 1 which are formed by reacting an amine with phosphorous acid in the presence of a strong mineral acid.
In Helv. Chim. Acta, 35 1785 (1952) various phenolic compounds were synthesized to study their complexing capabilities. Included were amino-carboxylic-hydroxybenzenesulfonic acid compounds by the reaction of phenolsulfonic acid, formaldehyde and iminodiacetic acid. Iminodiacetic acid, being a relatively unhindered secondary amino compound, readily gave a clean reaction (due to the single deprotonation at the amine and the amine group being connected the each carboxylic acid via a secondary carbon atoms).
The general trend in all of the above described efforts has been to form compounds having a multiplicity of functional groups in a configuration which enables them to be capable of chelating with metal ions. Thus, compounds with multiple functional groups exhibits enhanced ability of scale and corrosion control because they have greater complexing ability and/or solubility in aqueous solutions.
It is highly desired to have phosphonic acid compounds which are highly substituted and further contain other groups, including amino and hydroxy, in close proximity within the compounds structure. This combination provides a compound having good metal complexing capabilities.